Change how input/logging threads set their name.

Setting the thread name on every heartbeat uses a mild amount of
cycles and there's not much benefit to doing it there to get the
additional info regarding the number of processed messages since thread
names usually get truncated to 16 characters and omit that part anyway.

src/threading/MsgThread.h

@@ -199,7 +199,7 @@ protected:
 
 	/** Internal heartbeat processing. Called from child.
 	 */
-	void HeartbeatInChild();
+	void HeartbeatInChild() {}
 
 	/** Returns true if a child command has reported a failure. In that case, we'll
 	  * be in the process of killing this thread and no further activity